This invention relates generally to an apparatus having upper and lower cooperating cutters for longitudinally slitting a travelling web of paper, foil, cloth, plastic, metal or like material, the lower cutter or cutters being set in a desired position along the shaft thereof.
U.S. Pat. No. 3,583,270 discloses a slitter apparatus for traveling webs in which the lower cutters are driven by their own motors and are capable of being shifted over the width of the web to be cut to the desired position by means of an air cushion introduced to provide air bearings between the motor platform and transversely extending rails.
West German Pat. No. 10 38 902 also discloses a web slitting apparatus in which the lower cutters are displaceable axially on the shaft to which they are mounted for selecting different cutting widths, the lower cutters being in the shape of so-called cutting boxes having a plurality of cutting grooves presenting a series of spaced cutting edges. The cutting boxes are capable of being axially displaced a distance equal to at least the spacing between adjacent cutting edges. An annular, expandable tube is contained within each lower cutter which must be displaced together with the cutter during the shifting adjustment along the shaft. Thus, it becomes difficult to axially shift the lower cutters without binding or snagging caused by the embedded expandable annular tubes. Moreover, since the tubes are expandable in an uncontrollable manner the lower cutters could very easily be cocked on their support shaft thereby resulting in one or more lower cutters rotating about an axis at an angle to the rotational axis of its supporting shaft. Such results in an uneven quality of cut which is undesirable.
If, on the other hand, the expandable tubes of the aforementioned West German patent were embedded in annular grooves provided in the support shaft to avoid some of these problems, such annular grooves would only tend to weaken the shaft and cause it to sag when applying even negligible forces. The expandable tubes must therefore be positioned on the outer periphey of the hollow bearing shaft.